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Abstract
Executive Summary: HarvestChoice provides data, information and tools to support strategic investment decisions in
agriculture. Most agricultural processes are strongly influenced by biotic stressors, such as
insects and pathogens. However, available pest information has been lacking, for example
global maps of where pests and diseases could occur have not been available. To address this
deficiency, HarvestChoice has developed and implemented an approach to pest modeling
aimed directly at supporting strategic decisions in agriculture. The HarvestChoice system
includes methods, techniques and tools to both collect primary data on pest occurrence and to
model potential global pest occurrence. In addition, a global team of recognized pest and
climate experts has been assembled to aid in modeling, validation and peer-review.
The pest modeling system developed by HarvestChoice differs from the more typical
monitoring and prediction systems that support short- to medium-term objectives, such as
responding to pest events. Rather, we support strategic decision-making by mapping not
where pests occur, but where they might potentially occur. This approach allows us to answer
hypothetical questions that were previously unanswerable. For example, we can provide broad
information on what portion of the world’s crop area could be subject to a pest or what might
happen if a new variety were planted in a previously un-cropped location.
The end results of our efforts are maps of potential pest occurrence. These maps are
produced by modeling a species’ response to factors such as temperature and moisture, while
carefully keeping certain other factors exogenous (namely, those factors that might be decision
variables for strategic planning). For example, the models are not conditional on the actual
presence of a susceptible host, so our maps show the potential pest distribution assuming that
susceptible hosts occur everywhere, avoiding confounding the host climate responses with
those of the pest.
The models combine geo-spatial climate data and information on the seasonal
phenology of each pest to investigate potential growth, stress and persistence of pests on a
global scale. Growth is measured by a “Growth Index,” higher values of which indicate a higher
potential for that the pest’s population to grow at a given location. Potential growth is
restricted by sub-optimal temperatures or moisture and the pest’s survival is limited by
stresses, such as extremely cold or dry conditions. A final index, the “Ecoclimatic Index,” is
calculated by considering the extent to which growth is possible during the favorable season
and survival is limited by the stresses during the non-growth season at each location. The
result of this calculation, the Ecoclimatic Index is a measure of the potential ability of the pest
to persist and develop high population sizes at a location: that is, whether it can survive the
extremes of summer, winter, dry and wet seasons. This Working Paper describes the
HarvestChoice approach to pest modeling and places that work in the context of other pest
mapping efforts.